Macrophthalmus (Hemiplax) Heller, 1865

Barnes, R. S. K., 2010, A Review Of The Sentinel And Allied Crabs (Crustacea: Brachyura: Macrophthalmidae), With Particular Reference To The Genus Macrophthalmus, Raffles Bulletin of Zoology 58 (1), pp. 31-49 : 37

Macrophthalmus (Hemiplax) Heller, 1865

( Fig. 1C )

Medium-sized, up to 30+ mm carapace breadth; ocular peduncles short and stout, not projecting beyond lateral carapace margins, subequal in length to breadth of front or shorter; front very broad, not constricted between bases of ocular peduncles, where its breadth is ca. 35% the distance between external orbital angles; ischium of external maxilliped some 1.3 times length of merus; carapace with breadth ca. 1.5 times length, with lateral margins diverging anteriorly, with large, broad-based, pointed anterolateral teeth, branchial regions with rows of granules including oblique row extending from 3 rd anterolateral tooth to position above insertion of 4 th pereiopod and transverse row extending from tip of 3 rd anterolateral tooth; central region of posterior border of epistome straight; males without stridulatory apparatus; fingers of male chela elongate with index downflexed and a differentiated tooth only on dactylus; breadth of base of male telson <breadth of 6 th abdominal segment. Intertidal.

Hemiplax is a monotypic subgenus for M. hirtipes (Jacquinot, in Hombron & Jacquinot, 1846), restricted to New Zealand, the only macrophthalmid in that region. Its zoeal larval stage is similar to that of Heloecius cordiformis (H. Milne Edwards, 1837) (currently in the monotypic family Heloeciidae ) but is unlike those of the other Macrophthalmus species so far investigated ( Wear, 1968; Fielder & Greenwood, 1985), albeit that the larval stages of relatively few species are known.

Figures

Fig. 1. Form of the carapace and adult male chela of subgroups of the genus Macrophthalmus I: (a) subgenus Chaenostoma, (b) subgenus Euplax and (c) subgenus Hemiplax. Scale bars = 5mm.